1. Field of the Invention
The present invention relates to an imaging apparatus, and, more particularly, to a mid-frame for use with an imaging apparatus.
2. Description of the Related Art
With the advent of edge-to-edge printing, also known as borderless printing, various attempts have been made to reduce the occurrence of ink contamination of the printer mid-frame. As used herein, the term “mid-frame” refers to the supporting structure of the printer positioned opposed to the printing mechanism to provide support for the printing medium. In an ink jet printer, the printing mechanism is typically a printhead including a plurality of ink jetting nozzles.
A typical ink jet printer forms an image on a print medium by ejecting ink from the plurality of ink jetting nozzles to form a pattern of ink dots on the print medium. The printhead may include a plurality of nozzle arrays, such as a cyan array, a magenta array, and a yellow array, arranged as a longitudinal column of nozzle arrays. Such an arrangement of nozzle arrays will be referred to herein as “stacked nozzle arrays.”
Such an ink jet printer typically includes a reciprocating printhead carrier that transports one or more ink jet printheads across the print medium along a bi-directional scanning path defining a print zone of the printer. Typically, the mid-frame provides media support at or near the print zone. The bi-directional scanning path is oriented parallel to a main scan direction, also commonly referred to as the horizontal direction. The main scan direction is bi-directional. During each scan of the printhead carrier, the print medium is held stationary. An indexing mechanism is used to incrementally advance the print medium in a sheet feed direction, also commonly referred to as a sub-scan direction or vertical direction, through the print zone between scans in the main scan direction, or after all data intended to be printed with the print medium at a particular stationary position has been completed.
During printing, if wet ink accumulates on the mid-frame, then a subsequent sheet of print media will contact the accumulated ink, thereby smearing ink on the underside of the sheet of print media. In a conventional ink jet printer that does not accommodate edge-to-edge printing, the print engine controls printing so as to prevent the ejection of ink onto the leading, trailing, and side edge portions of the sheet of print media. In this manner, sheet margins are created on the medium sheet, which in turn protect the upper surface of the supporting mid-frame from ink contamination.
In order to accommodate edge-to-edge printing in the conventional printer, special media can be used that includes perforated tabs. With this arrangement, if a user desired a borderless print, the user would merely separate the perforated tab from the remaining portion of the medium stock carrying the print image.
In order to avoid the necessity of using special print media, further attempts have been made to accommodate edge-to-edge printing using regular, non-perforated, print media. One such attempt is to provide a hollowed out area located in the mid-frame in a region opposite to the printhead to collect ink that is discharged at the leading and trailing edge portions of the sheet of print media. An absorbent material is located in the hollowed out area to absorb the ink ejected thereon. A front set and a rear set of upstanding cockle ribs are positioned on each side of the hollowed out area, respectively, and extend upwardly from the mid-frame a sufficient distance to substantially prevent either a leading edge or a trailing edge of a sheet of print medium traveling across a print zone within the printer from making contact with the absorbent material. As the longitudinal extent of the printhead increases to accommodate more printing nozzles, such as in the case of stacked nozzle arrays, such a mid-frame design requires that the trough become wider. However, as the trough becomes wider, the risk that the sheet will bow and contact the accumulated waste ink increases.
What is needed in the art is a mid-frame design having improved surface characteristics. Preferably, such a mid-frame can accommodate edge-to-edge printing, and can accommodate printheads, for example having stacked nozzle arrays, without widening the extent of an individual waste ink collection opening in the mid-frame in a sheet feed direction.